The present invention relates to a wafer and manufacturing and reclaiming methods of the wafer, and more particularly to a control wafer or a dummy wafer and the manufacturing and reclaiming methods thereof.
In the semiconductor industry, the wafer for controlling the semiconductor fabrication is called a control wafer, and the wafer for maintaining the stability of single-batch fabrication is called a dummy wafer. For example, during the polysilicon deposition process in a furnace, the wafer for non-productive purposes (e.g., control wafer) and the wafer for productive purposes are put into the boat together to control the stability of batch-to-batch fabrication by measuring the thickness of the polysilicon deposited on the wafer for non-productive purposes. Moreover, the wafer for non-productive purposes (e.g., dummy wafer) and the wafer for productive purposes are put into the boat together to maintain the stability of single-batch fabrication. The wafer for non-productive purposes can promote the stability of the reactive airflow, so that the product can be uniformly deposited on the wafer.
For manufacturers, if the used control wafer or dummy wafer is not discarded as waste, then it could be reclaimed and reused as a control wafer or a dummy wafer. The reclaiming methods are described as follows. For example, Chemical Mechanical Polish (CMP) can be used to directly remove a deposition layer (e.g., polysilicon layer); however, the cost of such method is high (because the slurry is usually expensive), and the thickness of the wafer, will become thinner through the long-term use of this method, and furthermore, the wafer may be broken due to the mechanical stress in the polishing process. Other methods include Plasma Etching and Chemical Wet Dip that employs a HNO3 solution and a HF solution, for example. Both methods can also directly remove the deposition layer (e.g., polysilicon layer). However, the materials used to remove the polysilicon layer may etch the silicon substrate as well, so that the damage to the silicon wafer occurs, and thus the reclaimed wafer will not be suitable for use as a control wafer or a dummy wafer. Moreover, if the availability of the etching and polishing machines is limited, the used wafers cannot be reclaimed as control wafers or dummy wafers immediately, so the manufacturers need to additionally buy new wafers in response thereto.
Therefore, it is desirable to develop a new wafer and its manufacturing and reclaiming methods to overcome the aforesaid problems and difficulties in prior art.